L cells lacking thymidine kinase (TK) activity have been stably transformed to a TK plus phenotype by infection with ultra violet irradiated Herpes Simplex Virus (HSV). The TK activity expressed in these cells has the characteristics of the virus induced enzyme. HSV specific antigens have also been detected in HSV transformed cells. We propose to carry out the following studies on these HSV transformed cells: 1. Determine the factors which control the expression of TK activity in HSV transformed cells. The factors to be tested are: (a) the changes in TK as a function of the rate of growth of asynchronous cell cultures; (b) TK activity in mitotically synchronized cell populations; (c) TK activity in HSV transformed cells that have been infected by an HSV mutant that does not induce TK during lytes infection; (d) the effect of interferon on TK synthesis will be determined; 2. Determine the number of HSV antigens in HSV transformed cells. In addition, we intend to determine if those antigens are virion-associated on non-virion antigens. 3. Determine if human cancer cells contain antigens which have immunologic similarity to HSV antigens in HSV transformed cells.